Particle factory opens in Italy

Oct 10, 1997

The first of a new generation of meson factories was officially inaugurated in Italy at the end of September.

Called DAFNE,
the accelerator will be used for a range of experiments in nuclear and particle
physics. The facility at the Frascati National Laboratories cost about L100 bn (about £36 m) to build and
some 150 physicists from all over the world will conduct experiments there.

DAFNE consists of an injection system and a collider,
where electrons
and positrons circulate in two separate rings at 0.51 GeV,
before colliding
in the two experimental areas to produce copious quantities of phi-mesons.
These short-lived particles contain a strange quark bound to strange antiquark
and decay rapidly into other lighter particles,
notably kaons.

"DAFNE is the first of its kind worldwide,
the first so-called factory,
producing an abundant number of particles,
" says Paolo Laurelli,
director
of the Frascati laboratory. Higher energy machines producing B-mesons -
so-called B-factories - are planned for the Stanford
Linear Accelerator Center in California and at the KEK
laboratory in Japan.

DAFNE will have three main experiments: KLOE,
FINUDA
and DEAR. The KLOE
experiment will investigate the subtle differences between matter and antimatter
found in the decay of neutral kaons - mesons that consist of a down quark
and a strange antiquark or vice versa. When neutral kaons decay,
they violate
the CP theorem,
which states that the physics of an interaction should not
change if particles are replaced by their antiparticles and the interaction
is reflected in a mirror. Studies of CP violation could help explain why
the universe is dominated by matter rather than antimatter.

The FINUDA magnetic spectrometer will study what happens when an ordinary
nucleon composed of up and down quarks - such as a proton or neutron - is
replaced by a baryon containing a strange quark.

The object of DEAR is to produce "unnatural" atoms by replacing
one electron in an ordinary atom with a kaon. Spectroscopic study of such
atoms could lead to a better understanding of strong interactions and provide
more accurate tests of quantum chromodynamics at low energies.

Experiments on DEAR are due to begin next summer,
with both KLOE and
FINUDA taking data by the end of 1998. At a later date,
the facility could
also be used to provide intense synchrotron radiation in the ultraviolet
and soft X-ray range.